Laminated core structure



March 22, 1932. R M PFALZGRAFF 1,850,726

LAMINATED'CORE STRUCTURE Filed May 20, 1951 LAM/NAT/fl/VS INSULATED FROM EACH THER BY AN INSULATING L0ATIN6 0f? FILM lNCLL/D/NG A BAS/C IRON PHOSPHATE CUMPOU VD Inventov:

b Mow/46w His Attorney.

Patented Mar. 22, 1932 uurrsu sra'rss.

B058 M: PFALZGRAFF, F LYNN, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A COREIORATION 0F NEW YORK MMDTAEED CURE STRUCTURE application filed May 20, 1931.

My invention relatesto a laminated core structure for electrical apparatus.

In electrical apparatus such as dynamoelectric machines,transformers, and the like, it has been the practice heretofore in making laminated core structures to use an insulating varnish on the sheet metal laininations for reducing the eddy current loss in the'core. A good quality insulating varnish has cons siderahle thickness, and this reduces the number of laminations per inch giving a low space factor of the laininations. For this reason the decrease in eddy current loss obtained by the insulating material on the laminations is ofi-set lay-the requirement of higher flux density in the corsstructure resulting in increase in. core loss.

The ohiect of my invention is to effectively insulate the sheet metal laminations of a laminated core structure to decrease the eddy currentloss, and at the same time have a high space factor of the lamin.ations,ihereby requiring a lower iiux density in the core structure and ohtai ing a decrease in core loss I accomplish l by insulating the laminations from each 'o'her by an insulating coating or iilm, including hasic iron phosphate compound.

Further objects and advantages of invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the annexed to and forming a part of this specification,

In the drawing, the single figure isa fragmentary sectional View of a dynamo-electric machine provided with laminated core strucs embodying my invention.

" vided with slots in whichbare conductors 7 rteferri'ng to the drawing, 1'. have shown my invention as applied. to dynamo-electric Serial No. 538,883.

of a squirrel cage Winding are arranged and insulated therefrom by a basic 110I1 phosphate coating; as hereinafter explained. The conductors 'Z' are connected by end rings 8. The shaft of the rotatable member is arranged in bearings in the end heads 9 which are secured to the ends of the shell 2 in any convenient manner In accordance with my invention the sheet metal laminations 3 and 6 of iron or steel, or alloys thereof, are provided with a basic iron phosphate coating as described, for example, in United States Letters Patent No. 1,341,100 to Allen, issued May 25, 1920 or in any other suitable manner. In the above patent the article to be coated is immersed in a solution of dilute phosphoric acid with iron scales (iron oxide} dissolved therein, the iron oxide serving as a source ofjiron and hastening the chemical reaction to form an iron phosphate coating on the surface of the article which I have found has very good insulating qualities. In making the laminated core structures l and I prefer to use sheet steel punchings and generally these punchings have mill scale or iron oxide on the surfaces thereof. it is not necessary to remove the iron oxide from the surfaces of, the p-unchings as the iron oxide serves as the source of iron when the punchings are immersed in a solution, such as dilute phosphoric acid, which is capable of chemically reacting to form a basic iron phosphate coating. In this manner the iron oxide on the surfaces of the punchings essentially converted to an iron phosphate coating without any substantial change in the overall thickness of the punchings l have found an iron phosphate coating very eifective as an insulating material, and as it forms a very thin film on the contacting surfaces of the punchings, the number of punchings that can be stacked for a given physical height of core structure is considerably greater than when other coatings are used, so that a high space factor is ob tained. Thus the eddy current loss is eifec- 7 A for the core structure which reduces the core oss.

A. further advantage of my invention is the hi h heat resistingnproperty of the iron 5 phosp ate :coating. casting conductors in a core structure, aligned openings or slots are provided in the punchmgs and filled "with'molten metal, such as aluminum, which hardens after cooling to form conductor bars.

The iron phosphate coating does not break down when -heated by the molten metal and eflectively insulates the bars from the punchmgs. A reduction in load loss is obtained when an iron phosphate insulating coating is used in a castlaminated rotor of a dynamo-electric machine, the bars for securing the laminations together being spaced about the periphery of the rotor to form the armature 2 conductors, Under load conditions of the machine there is a tooth pulsation core loss due to tooth flux pulsations, and byhaving the rotor bars insulated from the punchings the magnitude of the tooth flux pulsations is decreased to reducethe tooth pulsation core loss, resulting in a reduction of load loss.

Although I have shown my improved laminated core structure as applied to a dynamo-electric machine, I do not desire my in- Y 80 vention to be limited to the particular arrangeinent set forth, and I intend in the followmg claims to cover all changes and modifications which do'not depart from the spirit and scope of my invention. 1-

What I claim as new and-desire to secure by Letters Patent of the United States is:

*1. A core structure for electrical ap aratus comprising a stack oflaminations, an means a including a basic iron phosphate coating for 40 insulating said laminations from each other.

2. A core structure for electrical apparatus comprising a stack of sheet metal laminations having an insulating coating including. a basic iron phosphate on their contacting surfaces. y

3. A core structurefor electrical apparatus comprising a stack of sheet metal laminations provided with aligned slots, said laminations I aving an insulating coating including a basic iron phosphate on their surfaces and their edges about the slots, and bare conductors in theslots in said laminations insulated therefrom by said coating.

4. A core structure for electrical apparatus comprising a stack of sheet metal laminations provided with aligned openings, said laminations having aninsulating coating including a basic iron'phosphate on their contacting sur- I faces and their surfaces about the openings 00 therein, and means including bars extending through the openings for securing said laminations together.

h Ini witness whereof I have hereunto set my i I v BOSS M. PFALZGRAFF. 

